AZ-900 Describe Azure architecture and services Practice Question
A company plans to run a large-scale batch processing job on Azure that runs for 10 hours every night. The job is fault-tolerant and can be interrupted. They want to minimize cost as much as possible. Which Azure virtual machine pricing option should they use?
⚠ Common exam trap
It's easy for candidates to choose Reserved Instances thinking they always save the most money, but they fail to recognize that Spot VMs offer even greater savings for interruptible workloads without any upfront commitment.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Spot VMs
Spot VMs allow you to use unused Azure compute capacity at a significant discount (up to 90% compared to pay-as-you-go). Because the batch job is fault-tolerant and can be interrupted, it is an ideal workload for Spot VMs, which can be evicted when Azure needs the capacity back. This minimizes cost while meeting the job's requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Reserved Instances
Why it's wrong here
Reserved Instances provide a discount for committing to a 1 or 3 year term. However, they are not cost-effective for a nightly 10-hour job because the reservation covers the VM 24/7, even when not used.
When this WOULD be correct
A company runs a critical, always-on web application that requires consistent performance and uptime, and they can commit to a 1- or 3-year term to achieve the lowest possible cost for that steady-state workload.
- ✓
Spot VMs
Why this is correct
Spot VMs are the cheapest option because they run on unused Azure capacity at a steep discount (often up to 90% compared to pay-as-you-go). Since the described batch job is fault-tolerant and can be interrupted, it can handle the eviction notice Azure gives before reclaiming capacity. This makes Spot VMs the ideal cost-optimization choice despite the risk of eviction, as the job can simply pause and resume later.
- ✗
Pay-as-you-go
Why it's wrong here
Pay-as-you-go (PAYG) charges per second for compute capacity with no upfront commitment, making it flexible but relatively expensive for sustained workloads. Because the batch job runs for 10 hours nightly and can tolerate interruptions, Spot VMs offer the same compute capability at a fraction of the PAYG price. Choosing PAYG would ignore the workload's fault tolerance and forgo significant cost savings.
When this WOULD be correct
A company needs to run a critical, non-interruptible application 24/7 and requires maximum flexibility with no upfront commitment or long-term contract. Pay-as-you-go would be the correct choice.
- ✗
Dedicated Hosts
Why it's wrong here
Dedicated Hosts provide physical servers dedicated to a single customer, ensuring hardware isolation for compliance and licensing requirements. They are the most expensive compute pricing model because you pay for the entire host regardless of VM usage. For a purely cost-sensitive, interruption-tolerant batch job, they would dramatically overspend and provide no benefit.
When this WOULD be correct
A company requires compliance with specific security or licensing policies that mandate dedicated physical servers (e.g., for a regulated workload that cannot share hardware with other tenants).
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Spot VMsCorrect answer▾
Why this is correct
Spot VMs are the cheapest option because they run on unused Azure capacity at a steep discount (often up to 90% compared to pay-as-you-go). Since the described batch job is fault-tolerant and can be interrupted, it can handle the eviction notice Azure gives before reclaiming capacity. This makes Spot VMs the ideal cost-optimization choice despite the risk of eviction, as the job can simply pause and resume later.
✗Reserved InstancesWrong answer — click to see why▾
Why this is wrong here
Reserved Instances require a 1- or 3-year commitment and are not designed for interruptible workloads; they provide cost savings for steady-state, predictable usage, not for short-duration batch jobs that can be interrupted.
★ When this WOULD be the correct answer
A company runs a critical, always-on web application that requires consistent performance and uptime, and they can commit to a 1- or 3-year term to achieve the lowest possible cost for that steady-state workload.
Why candidates choose this
Candidates may think Reserved Instances always offer the lowest cost, overlooking that Spot VMs provide even deeper discounts for interruptible, fault-tolerant workloads.
✗Pay-as-you-goWrong answer — click to see why▾
Why this is wrong here
Pay-as-you-go does not offer the deep discounts needed for a nightly 10-hour batch job that is fault-tolerant and interruptible; Spot VMs provide up to 90% cost savings for such workloads.
★ When this WOULD be the correct answer
A company needs to run a critical, non-interruptible application 24/7 and requires maximum flexibility with no upfront commitment or long-term contract. Pay-as-you-go would be the correct choice.
Why candidates choose this
Candidates may think pay-as-you-go is the cheapest option because it has no upfront cost, but they overlook that Spot VMs offer significantly lower rates for interruptible workloads.
✗Dedicated HostsWrong answer — click to see why▾
Why this is wrong here
Dedicated Hosts provide physical servers dedicated to the customer, which is expensive and unnecessary for a fault-tolerant, interruptible batch job that can use cheaper shared infrastructure.
★ When this WOULD be the correct answer
A company requires compliance with specific security or licensing policies that mandate dedicated physical servers (e.g., for a regulated workload that cannot share hardware with other tenants).
Why candidates choose this
Candidates may think Dedicated Hosts offer better reliability or performance for long-running jobs, overlooking the cost and the fact that the job is fault-tolerant and can be interrupted.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Azure virtual machine
An Azure virtual machine is a software-based emulation of a physical computer that runs in Microsoft's cloud, allowing you to deploy and manage applications without owning the hardware.
Key term
Workload
A workload is any discrete application, service, or function that runs on a computing resource, consuming CPU, memory, storage, or network capacity.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.